Trunking system for radio distribution



v rv l v J, 96e. ll, 1928. I 1,695,182

E. E. CLEMENT I TRUNKING SYSTEM FR RADIO DISTRIBUTION l Filed Harsh 15. 1926 7 Sheets-Sheet 1' """l""l H\\N D v l q i l i-^r`l N 5 :il )j u :mj-:tim mi 1 Mk W w lv WNW Silk I5? IIJ! ILlu-l-l U Dec. 11, 1928.

' 'E. E. CLEMENT TRUNKING SYSTEM FOR RADIO DISTRIBUTIDN Filed March 15, 1926 7 Sheets-Sheet 2 De.; 11, 192s 5 o 17010 62 lf E. E. CLEMENT TRUNKING SYSTEM FOR RADIO DISTRIBUTION Filed' kann 1s, 192s fooi 7 Sheets-Sheet 3 "510 72:57' TRUNK IIUI Dec. 11,'192a Masas/ace :s

orar/mv zo UZ @maw- E. E. CLEMENT Hammer TRUNKING SYSTEM FOR RADIO DISTRIBUTION Filed March 15, 1926 .7 Sheets-Shoe? 4 Dec. 11, 1928.

Filed March i5. 1926 7 Sheets-Sheet 5 a A. A

e ,m u 4 w a o ,o .w m 6 .w p M a e o .Kb 02 2 6 H2 m M 0 Ww IU j llz .o 7

Dec. 1l, 1928.

E. E. CLEMENT I TRUNKING SYSTEM FOR RADIO DISTRIBUTION Filed March 15. 1926' 7 Sheets-Sheet 6 |n... .IlNI

SK. am

Nlku

Dec. ll, 1928.

TRUNKING I, 5am/v uur E. E. CLEMENT SYSTEM FOR RADIO DISTRIBUTION Filed March 15. 1926 '7 Sheets-Sheet 7 Patented Dealj, 1928...' y zal and las for its object to organie such a s'ysf tcm so that azprovram in aybe originated,

relayed and distri 1 tcd over a large area,

uni ormly and in `a s stcmatic and orderly 0 manner tonauthorizei users or, subscribersv who will get the full benefit of the use'pi vacuum' tubesin receiving and amplifying. without the necessity--of maintainn tubes at their stat-ions, the tubes u sed by t e 'sub-, 5. scribers in receiving being located at central points. where g supervision, maintenance, power suppl and control may be centralized and p ut un er the care'of vexpert operators.'

, In the second t0. to, both relay distribution and supervision of the broadcast service for a group of sub-f scribe'rs is' carried on at the central statioii E. cLian-NT, oF'wAsHINGToN, DISTRICT or co'LUrrIIAf lissINon'T EDWARD FgcoLLaDAr, or WASHINGTON, DISTRICT or coLUIaBIL-f #l fgf f f- 'a the aforesaid in that a districtrelajjgl stalf f the standard multiple cnits .of fan ordinary telepl1on e exchangeg. system 1n which J-J' are. line t'erminal Y.'

'aL-ks forrninL'tIIe terminals of telephone.' ities leading to stations to be interconnecteda such as the subscribersstation A'. Thes Jacks' fare arranged t 'be interconnected: 7 9

throii'gh `the usilalf'ailspfering' and calligi plies' .P7-P. f el'niinsth terminals Qith. if

I usual x :`o1nn1on battery cord circuit shotvn' l application above referred The central olice trminals o: each line are amp L and 'cut-oil' relay L. There serylq 1s to be metered a 'recel-dino' meterM is als?.l

or exchange localfto. the group. The sub- A individually associated with the line."L Thus,

ject o f theipresent. application lii'ers from.' the circuit arrangement here shivn as that.

tion, common to seve1'al s ubs' crbers central' Inon'ba'ttery, te ephne exchance system, and

stations, is provided fnjI receiving b ro'adtast matter furthe central stations by radio, the

central stat-ions' distributing the broadcast: fre'd and brought -out, later inthe descrip?" A as suchisjrell understood in the art further.; detalled descriptionthereof will be here def,

' the central stations is had attire district :felay station o 'ijer individual-telephone lines the telephone exchanger portion the broadcast dst1"rbt1n'g )oigtion .of a 'subsibers' centrale-afi?? @alias Per? .simi

Sstm s applied 10.152. distrit- ',ccntin'ng several :local r ,exchange gronpsr, n q.

wire, while'sup'ervision of .the reception eti lineztermial, niultiples 1, 2 and sentlng mult1pl 'e s o f th e tip, sleeve and testi ductors 5 and 6. lIn

or cut-0E circuits, respectivel{v, 1 provide'i:

fics ndalilietes Withril, Slibscriberfs isle? f v.' p one lme` erxnmal apparatusoftherteleft dot't'e'dline in 2 is situated at. the, 12'! subscribers substahon and .connected the subscribers telephone substation a para-l;

g- 2th? subscrbes' hne multiples 1 f-2 terminate in thespring 19g plug 10 to be spread apart to'en'gage withth stationaryl contacts 11-12 to extend the coli fi-i iFis-5.1%'siasraeshawnsan.emessi. secties.atthenaltass .1 -'T2 to. conductors@ switchboard, coins,

le is situated atthe centrlfof f 95;;

contacts Z1- Bof 'a ja'clr9 which contacts are'. arranged jupon the Insertion Qithedux frozn'tli'e distritzt station-to. other central i stations equipped like that of Figs. 1 and 2,' said trunks and order circuits terminating at `the dist-riet station'in jacks'Sl, 83, 'etttl L5l situated-With the jacks 50, 72, before th' test operator and accessible to the plug 80.

To enable tests to beniade of a relay appa-- ratus. at 'the central office with all lines i disconnected therefrom but without interle rupting the service, the central olice may bei provided with a duplicate relay apparatus 89 arranged to be connected tothe busses 27-28 by closureof a switch 70 when the apparatus -29 is disconnected by opening the 5 switch 71, for testl purposes;t.n,i'.l .11i-:1.5i Before proceeding with the description of operation ofv the system a`broader`view of i the system is advantageous and niay be had I by reference to Fig. 4 wherein the district.. 0 station 38 is indicatedV as being operatively. i associated with 'several local groups or sub. i scrihers distributing centers 91, 92 and 93, l cach equipped as indicated in Figs. V1 and 2.. i The district station is arranged to receive' f .5 broadcast matter from an distant station I and relay the same by ra io to the seYeral i subscribers distributing centralxstations 91,. 92 and 93 as indicated by the arrows adjel cent to the'antenna symbols-onthe several 't0 stations. vThe station 91 represents the station diagranimed in Figs. 1 and 2 while the I substation A. represents the station A of Figs. 1 and 2. Also the various lines and trunks 69-70, 15G-.151., 152.-.-153, etc. re )re-- 5 sent those correspondingly numbered in igs. 1,2 and 3eme. .faz-"tseii 'In operation,.broad ast matter is transmitted from .the'..d.istri ct .station (Fig. 3) by radio'to the'relay apparatus at the -diierent central stations suchV as the relay and .distributer 29 (Fig. 2), the` audio -output .cir-f cuit of which is `connected .through-switchl 71 to' the busses' 27.-28.- A subscriber at substation A -desiring broadcast service, now. i connects his broadcast receiving' or extension set'A to the line by inserting thereceiver plug-P2 in the jack J. which connects his. receivei` 64 across the linemultiples 5 and 6. through the 'booster 4coil windings. SOT- 6 5 i and condenser 66 in series., and closes a path for' .direct .current betweentheqmulti lesoand 6 .through coil 60, lower sp1-ingo jack J?, transmitter 62 -and signaling key -,63 f'; i. This energizes the subscribers line relay at the central otiice in the usual mannerby l current from the central oice,..cou'1mon battery. B, conductor 68, right handwinding of relay L', line conductor 69, to subscriberls substation A', line multiple', to subscriberfs broadcastreeeiving set- A19 Fig 2),ico1l 60, transmitter 62, contactso key .63, cen-. ductor 6, 70, .left hand wmdlng of line relay L'- and back .tobattery QB. ,Actu'ation of the line relay energzes the lm e la-mp Igbyf i closure of a local circuit'which :may be traced from common batte B through circuit ele# ment-s L, 7l, 68, and ack to battery B. This; causes tl1e';l.ine.lamp-L'"i1t thetelephone; operators switchboard to glow, but only or a moinent, as the subscriber-wanting broadl castserVi-:e will immediately operate his sig,"v nal key 'to rapidly open and close his 'line circuit which causes his'line lamp to flickerinstead of glowing steadily and so indicate t0' the telephone operator (Fig.1) that the 75 subscriber is not calling for a telephone connec-tion.` This intermittent actuation of the subscribers telephone line relay L' Aalso Y causes a tlickerinff of the lamp 36 (F ig. 2)

- associated 'with his broadcastservice, lnul- 80'.

tiple jack '9 situated before the broadcastl service operator. Thisoperetor perceiving the flickering of the lamp interprets the signalV as a call -for broadcast service and in answer thereto inserts the actuatinnr plug 1 0 85i in the jack-9.1 This effects the closure of;` contacts 7--11, ,S4-12, and 33. Closure-of the contacts 7.-11.`, 8-12, connects the bat`. tery B (Fig. 2) aeross .the subscribers line throu'h the repeating coil windings 15-16 9G and the sleeve. supervisory relay 42 which' connect-ion may be .traced from battery B (Fig. 2) throughcircuit elements 15, 13, 11',- 7, 1, (into Filg. 1), 69, 5,- (into Fig. 2), 60, 62, 6, (into "i 8-12, 14, 42, 16, back 'to battery B.' As this completes the circuit including .the battery; Band the relay 42, this relay is energized. and closes the lcircuit of the cut-0E relay LF (Fig. 1 over a path which may be traced. from the" common battery B (Fig. 2).- through the circuit elements 35, 34, 3, (into Fig. -13,.cut-o`' -relay 145,68, and through groun back to common battery B. Encre. gization of the cut-oil relay disconnects the subscribers line from the telephone line signal apparatus in th'e usual manner, thus .causre f ing the ,line lamp' L to become deenergized, and extinguishin both signal lamps Lzand;

36. Asthe cut-o relay is held energized over, 11a

the testj conductor ,3 by battery supplied;`

thereto through the specialtone test device- 3 5, .ai telephoneoperator-in testing the line, will receive this, characteristic tone test inl-3 stead of the usual click in the ear indicating that the subscribers .line is .busy .wththe special or broadcast service which maypor` may not be interruptedor telephone A.service according to the wishes of the subscriber.; Energization of theirlay 42 (Fig. also connects the vinput circuit 4of the subscriber'fsg' line tube. 37 t9. thebrodcast busses2r28. by way ofcontacts 23, v24 and. co 1 1d\1c tor,s i 25,26, respectirely. The actuatmn oflrelay 42 also' energiaes .the .subscribersline 'lamp 125 37 by `closure of. its filament circuits tliroucr contact 35.1, andejilament .batteryFv 'Ih -atten .13"Y thevehihe' Pleteitcaitfselif decors.. 2.1i, 22.1.19@ arrancaron nemers m g. l), 70, 2, (into Fig. 2), 9U

17 and 18. T hus the 'broadcast matter supi plied to the input circuit of the tube 37. from the busses 27-#28 is amplified in the output circuit 22, 18, B6, 17, 21, and transj-ferred into the subscribers line circuit by the repeating coil windings 15-16 included in the linev circuit. The broadcast signal cur rents passing through the Windmg 60 of the.

tact 31 and energizes the 'radio service signal lamp 36 over a circuit which may be traced from common battery B through circuit elements 31, 32, 33, 4, 36 to ground and back to common battery B. This causes the lamp 36 to glow steadily indicating to the broadcast service operator that a disconnection is desired whereupon the operator pulls the plug 10 which o ens all the contacts of jack 9 and restores t ie circuits to normal. f l -V Vhen it is desired to originate broadcast matter at the district station (Fig. 3)', Inicrophone 40 is used which operates through a modulator and transmitting portion .of the radio relay 39, the circuits and apparatusl of which modulator and transmitting portion of the relay being of any known or other suitable type. Where it is desired to permit a subscriber to broadcast from his substa-J tion he may be connected through the ordinary telephone exchange circuit (Fig. 1)l

to the telephone line circuit 101- 102 termi' nating in the multiple jacks 38 and 138 at the. district station (Fig. 3) from which the connection may beextended by plug 48 to the modulator of the relay transmitter 39.

Toenable the operator at the district station to listen in on the broadcasting subscribers line, the listening set 46 may be connected to the line through the plug 47 and the re' maining one of the multiple jacks 38 and 138. 'f 1.' "i1 :tw-#xi 'A test Aof the quality of reception at the centralstation (Fig. 2) may be had from" thc district station (Fig. 3) over the testing trunk 150-151 through'the jack-.and

the plug connection 50 and 47, and the lis-i tening set 46, the testing trunk having been connected with the output of the receiver 29 (Fig. 2) through jacks 51 and 72, and the link circuit 57. If itvis'desired that this test be made on the output o f the receiver 29 free'of all subscribers line connections'- a Vduplicate relay transmitting apparatus 89 may be put into' service and connectedA to the distributing bussesby closure of'switcb; 76 before opening the switch 71 toclear the apparatus 29, thus preventin interruption of the broadcastnservice. d ther tests of.

theoutput'circuit 'or other portions of the. 7

apparatus at thecentral station -may bei made over the testV trunk by connecting the operators testing apparatus 59 (Fig. 3) through the plug 8O and jack 50 to the test trunkit being understood that the appa-,7,5l

ratus 59 maydconsist of suitable testing` on., measuring instruments such as a sourceor" sources of current, amm'eters, voltmeters,A etc. In making these tests, the operator at the district station makes use of his listening set 46 and the ordercircuit 152-153 rto communicate 4with the operator having charge of the broadcast receiving apparatus4 at the central station, so that the latter operator may set up the various circuit con'- 85 nections necessary to make the tests.-

I have. illust-rated and described hereiny up to this point,'a system in ,which a single. broadcast relay apparatus is provided at the'relay stationshown in Fig.l 3, and a 90 single program bus 27-28 with single line switches or jacks 9 atthe central distribute. ing stations.; Itis of course' obvious thatv these elements may be multiplied, that `is to say, that the relay distributing station shown in Fig. 3 maybe equipped to receivei simultaneously from several sending stations, or may be equipped to receive from, one or more sending stations and simultaneously to originate matter for distribution among the several district central stations; shown in Fig. 2.; Each central station would then have a number of receiving instru-.i ments 29, adapted to. receive the diierent programs, and the output of each of these receiving instruments would be communicated 'to a separate trunk so that there would; bev a number of program trunks similar to' that shown in Fig. 2 at 27-28, to any of which the subscribers ma have access. For this purpose, the switching apparatus disV close in my t'wo prior copending applica-fA tions, Serial No. -754,406, ,filed December 6,Y 1924, and Serial-No. 913, led January 6T,- 1925 Vmay be employed. Asimple form of selective apparatus working in conjunction'. with the line switch 9 is` shown herein in: Fig. .5.4 Inv the arrangement of this figur,-

the subscriber calls as before giving one l lon'g closure for a' telephone call, and ay series of short flashes for a radio call. This may be done by means-'oa key 63 '(Fign 2) or the ordinaryautomatic sender well known to those skilled in the telephone art; At the telephone station 'A' of Fig. 1,;it is;

unnecessary .to have any key or keys to se-'l cure telephone connection, '1t` is only neces; sary to remove the receiver from' the switch-1 hook,as usual, 'this producing a continuo lau ' Referring to Fig. 5, the partsare exactly the key-63,tl1e relay 42 .is energized andv as in Fifr withciception that a. As 'ele'v cioses l l t s" onta'ct s 3150, '34, '24, 23 and 351. si'vitcliprovided, stepped' around; by This connects `the input'or grid side of the "means of anelectr'magnet 420, controlled "line 'tube'37 tot-he s'vvitchwipers' s?, and also i t5 through rontcontaotslOfof the relay 42 closesnthe 'filme'nt' circuit through battery",4

u jhichisincluded in :the lineeircilit oflpat- 'I `h e fth `ee pairs of bank contacts "s'-" tcry B "when'the contacts of thelineswitch 2s-a? Vrepresent a suitablnumber 'to contain 9 areclosed by the radio operator. Th se all 'the program busses, and if it bedesired l'etivesvfitch S contains ,bank contacts' eto 'u'se"a 'circ1'e of contacts 'greaterin number loef-a? connected to vsepan-ate busses 27-28 than the number o f busses, then the latter 75 (arrymg No. Il program), 270-280 carliiay be repeated several 'times in passing" rying No. 2 program), and 2700-2800 `ca ,rfnroundthe vcircle'. The switch n'iper're rying No, 40, or aunouncemeuts)..' The 'f leftjvhelfe theystand Without'restoringfso switch S (loesiiot need tobe 1 e`sto`red'to zero, that when 'the subscriber has become4 'con- Y5 and ma f be left always in the last position 'nfected through the tube 37 to theswitch '$.80

to ivhic 1 it hasbeen moved, since the wires 'he'is immediatel on some bus. If it 'i's'a"' 2 5- 26 leading to the wiper arms s of the .program b us an he desires .to select soine switch are'cut-oif at the relay 'cont-acts 2 3- particular item, he Canby means of his key 24 when the apparatus is in disuso. The No. 63 propel the's'witch arms a unt-i1 theyr come 201 and No. 2. program' busses are connected 'contact witlftlle banki contacts s con- 85 -to the output circuits o f broadeastrelay-ief iiected tn the announcers bus 2700-2800,l 4 c civers 29;- 290 respectively and the' an- 'and by listening, he 'will hear' a continnoun'cement bus 2700-2800 1s connected to uousannocementj of the items then upa local distributing apparatu'sor amplifier "fon the bus, the items to follow', the,- numf5 with amicrophone'lf.. The announcement fers or" call letters` of thestations from 90 set as a ivhole is connected symbolically only y'vhieh the said items are being sent, and tit-AS.- This position .or equipmenton the any other 'interesting f information conradio switchboardcorresponds tothe .infornected vith the same. I "consider this mation operatorfs p'sitio1ona telephone separatef announeementbus, corresponding switchboard. f,, kr -..L` .f to' 'an information operators position, to," The operation of Fi 5 'is as follows': the be important as well as novel and original subscribercalls as be 01ebyfmakin0 short jy-ith 'myself and shall c lail'n "the samjcclosures of his line at the key 63 after in leo'rdin y. Having ascertained what 'pro- 'serting the .plu l?? in the jack .l".;'.'Tl1ese' g'iam and 'what items he desires to. hear, the

.-35 short .closures ash both the. telephone and'fsub'seriber; is ableto start vfrom zero and ste .100

.50." ing up and down betweenthe pairs ofcon-Qfnleans thatduring' 'the entire broadcastn "L". 'line circuit remains closedaftersignaling s lilled time the radio switchboard lamps (Fig. 1) 'andi.. the"svvit o h around to 'the desired busses suc 36 (Fig. 2). Connection ises'tabhshed'byfas' '27j-28 "27 0-280, "^et'c. Thus thalianthe radio operator inserting the plug 10 in fnouncers bus, vvhen reaehed,'whioh 'is althe jack 9, or closing the'equivalent s'witch. \vays eas1ly distinguishable, serves a double 4 It may be mentioned in assing that any purpose, 'bein'g'alsothe zero bus from which 105 form of switchmay be sustituted for the; the rodram busses'are counted. If thesub. jack 9, even to a rela controlled frm a. 'f'sc-ri er has 'a loud speaker l and desires seine keyboard Aposition by't e'oper'ator, without particular item-for which lle has to Wait, he departing from theinvention.- Divers or'ms 'may leave` his switch connected with the an- .45 of switches suitablel for this purpose, will ,oe- Y nouncersfbus until 4the time fornnakingo 110 'our .to those skilled in the art, such as fon 'ex- "neeti'n' arrives', and 'inthe meantimgmll re-" ample, a key switch o f the general 'type pf `jc`: ve all the annoiinc'ements, l.ivitlysuch l`t operators ringing and listening key, hav tes f eptertamrnent'and in rma'tioh ing pivoted lever and a rockingwedge pass- Ifn'ay h 'e Y intercollated therebe Ween? Thr tact springs, to open and close tliem. S uch `pri od, the announcements 'will befgoing on, a switch may .have practicallyA any..desired interspersed yiith co1nments,ex`pla1 iat1on number of contacts, and requires no sepa-.etdf ofthe's"e .1 1 n(lybe added'neivs .rate plug to operateit. The. additional eonthe l iijre,if desire butl think it'pre'e'rable 55 tacts are available .for a numberof purposes, to have theseV 'on a se l including the cutolf o fbattery current from leaving' the announcer s bus to ulfill the* the magnet 420 .when the parts are in disuse function of aninformatonoperator only. -a which should be done as a matterof goodf,v Ihav'e 'sho'wnherein 1n Fig'. 1 'a nt're'on- "practice, although,no t x`1eees s ar1l y a part of nected lto the testor cut-oil 'wire 3, and for the. invehtionpl-:r: iii )f'fi-l r-iflytf. operated. 125 The subscriberslinehaving been ths eon" '1n 't e ulsual mannen 'For metering ehefrau-'1 neared with the central pince wires 1 -'2, the dio service, I have shown in Fig. 2 meedinrelay 42 is included therein, and cornes n- 1."Ifii'ut2'\ t and high ,Voltage generator dap der' the control of the subscriber.. Since his ,ed,to'rneter operat1on, in a inanier familiar This generato; 13

'aratefpro" rain b'us 12- rf 'i "-1.: '-.fi f1 U... r i Y only connected 'wit-h the relay 42 is ener such frequenciesfbiitffmay' employ also sugized and the commutator closesthe circuit, per-audio frequencies, so long as theyI are which occurs at intervals during the time suitable for line transmission. In the work the subscribers line is connected to the raheretofore doiie by Major General Squier d10 bus lor busses. I have also shown a 'and others, frequencies rangiug'from 25 to70 meter operating generator and commutator v100 kilocyc'les per second have been found 4in Fig. 5, but it is to be understood that in suitable for this purpose. In order to make the latter case, Where there is selectioirof such frequencies available for distribution program, there should alsobe selection of a. among the subscribers in 4the present sys- H) chargingrate lcorresponding thereto; which tcm, the co'nnectionsfrom the central stationi75 means tliattliere would be a separate meter receiving and relay distributing apparatus coniinutator for each of the program busses, remain practically tliesaine, as "those debrought into connection with the contacts 34 xscribed and shown in F igs. 2 and 5, the inand test wire 3 through bank contacts of the put or' grid circuit of the individual' line switch S, corresponding to the program con- Vtube 37 also"reinaiuing the same. The re- .tacts s-.s-s2 associated tlieie\vith,l, by adpeating coil connection to each 'line must )listing these separate coininiitators to difeither besi'ippleniented or replaced however ferent speeds or rates of o eration, the meby a ,filter connection, preferably permanent, tering can be made varia le according to \\'hich` \v ill permit superaudio frequency cur,A the program being receiyed. This is derents to be transmitted from the plate circuit' 85 scribed and claimed in my. prior copending of thetiibe 4to and over the line circuit to the applications, Serial No. 746,357, `filed Octosubscribers station, While the battery curber 28,1924,` and Serial No. 746,358, filed rent from the battery B will simultaneously October 2S, 1924.' Any method of diierflow over the subscribers line for signaling. .eiitial metering may be'einployed for this and talking purposes of the subscriber. '.At 90 purpose Without departing from the scope the subscribers station, complementary con of my invention. .ff' ii ections 'must be made, and a detector radio It should be stated here Athat while ,I have set must be connected to receive 'superaudio ,developed herein a specific arrangement of `currents over the line, While the telephone, o the acp Jaratus and circuits for the purposesl elements are connected, preferably in par" 95 state there are a number of modifications, allel, to receive the battery current 'and whiclrI contemplate and shall not describe transmit and receive audio frequency waves. herein specifically, because they will form Such an arrangement is shown as to its printhe subject matter of separate a plications. c iples in Letters Patent granted me January. I wish to state herein however, t at accord- 6, 1925, No. 1,552,362, to which reference iS 100 in'g to one modification, the line signal lamp had for .further explanationy of the -princi- 36 on the radio switchboard, and the line ples inyolvelK ff ''j'- -vacuum tube ,37 on, the same 'may 'be Th'e'arrangernent of Fig's.' 6 and7, is the and preferably are, made one an the same saine as that of Figs. 2 land 3, 'except thatunit. The tubes 37 are used as amplifiers, the rela s '29 and 89 (Fig. 6) are arranged' '105 which means that they will be lighted to to take roadcast matter at their input tersomewhat greater brilliancy thanif used 'as Ininals 'at line frequencies such as audio or detectors, hence under proper 'conditionsof mpdulated superaudio, and the relay translighting and arran einent,theymayverywe1l initter 39 (F1g..7) is arranged to transmit-l .be for visib e signals. According to' a't suchline frequencies andhas its output 110 this arrangement, when a subscriber calls 'circuit 'connected to multiples 351, 352 radio, he will flash the filament'ofthe tube 1 through which its out ut is'distributed to 37, which gives the visible signal to the radio the 'relays 29 or 89 o different local disoperator that he desires radio connection.` tributing stations sch as that of Fi6 t rouv 115 The tube 37 for such use would belocatedmineans of circuit connections made' in a desifmated and determinate'position to@ connecting cords or links such as 353 Flg. indicate ltbhc identity of the line, and wouldL '7) tr `unk '1 50, cord 57 (Fig. 6) and jac 55. 'preferably be associated with theline switch' Inprder to keep the power outputproppr- ,i ,9. When the'plii is in or throws the'switch'gftional the number o f connected outgoing 'i5 9, the result wou d beto cut oi the direct tif unks, each linkcircuit 353'is preferably 120 1 in e connection with the tube 37,' and `sub-' fpro vided' vvitli ai'i'mplifier. Itis preferable stitute the; 'workin circuits through the' to'traiisinit from the district station to the @tubes as shown in ig. 5. In'clearing out'jcefntral station' by' supera'udlo or carr1er` I. the subscriber may then a ain iash the la- `'current' in which case the relays 29 at the nient ofthe tube 37, wliic witlithe s witch central stations (Fig. 6) are preferably 'ari 125 9closed, would indicatedisconnectiom "frra'nged to detect th'e'sa'me' and supply the f While I have herein described and illusaudio currents'amplified to the bus 27-28. ltrated the use o f audio frequencies fordisy nWhat I claim is:` f .t= fa-:ff tribution to the subscribers over' theirwired 1 a system of radio broadcast d istnbu;

line circuits the invention is not limitedto'tion, a plurality of subscribers stations dilfl30 Cil for receiving the vided into a )luralit of groups, a district broadcast station having broadcast receiving apparatus and wired broadcast distributing means common to said groups, a central station for each grou having receiving means radcast from said common districtstation, amplifying means arranged to connect the receiving means of a central station with said distributing means, and amplifying means arranged to connect each subscribers station with the receiving means at the central station of its group.

2. In a system of broadcast distribution, a district broadcast service station, a plurality of local central stations, a group of subscribers stations for each central station, circuit connections between said central station and its group of subscribers stations, circuit connections between said district station and said central stations, means at the district station for amplifying, and transmitting broadcast matter to said central stations over the circuit connections between the same, and means at a central station for amplifyin and relaying the broadcast matter receive thereat to its subscribers stations over the said circuit connections bet-Ween the same.

3. A s stem for the broadcast distribution of signa s comprisin the following instrumcnt-alities: aplura ity of subscribers stations distributed over an extended area and divided into roups, a central station for each group, wlres interconnecting each central station with the subscribers stat-ions in its group, a district station common to all the groups, wire circuits connectin the district station with the several centra stations, means at the district station for receiving broadcast matter from other stations and means for amplifying and distributing the same over said Wire connections to the several central stat-ions, means at each central station for amplifying the broadcast matters received thereat, and means for connecting the subscribers Wires to said amplifying means whereby the receiving and distribution of broadcast matter is eii'ected through a single station, but its amplification in distribution "l 1,695,185" .i f1 g 7 is proportional to the number of stations served.

4. In a system of radio broadcast distribution, a plurality of subscribers stations divided into a plurality of groups, a central 'station for each group, a district broadcast station having Wire trunks extending to the several central stations, means at said district station to produce modulated carrier current suitable for transmission over the wire circuits, means for connecting the same through amplifiers to said Wire trunks, program busses forming terminals of said trunks at the several central stations, and means to connect the subscribers lines to said program busses through amplifiers.

5. The combination of a central station and a subscribers station, with line Wires interconnecting them, a vacuum tube amplifier at the central station associated with the said line Wires, a source of broadcast matter, and means to connect the subscribers line thereto throufh said amplifier, and other means controlled by the subscriber for controlling the filament circuit of said vacuum tube to fiashand put out the same, by way of signaling.

6. In a system of the class described, a subscribers station and a central station, a vacuum tube at the central station having a filament circuit, means for transmitting from the central station through said tube to the subscribers station andmeans controlled by the subscriber to produce changes in said filament ,circuit for the purpose of signaling to the central station.

In testimony whereof I hereunto aix my signature.

EDWARD E. CLEMENT. 

